Electromagnetic forming apparatus



Nov. 24,, 1970 wEADoc JR ELECTROMAGNETIC FORMING APPARATUS Filed July 12, 1968 2 Sheets-Sheet 1 IN VEN TOR.

BYWXM I ATTORNEY Nov. 24, 1970 R. WEADOCK, JR

. ELECTROMAGNETIC FORMING APPARATUS 2 Sheets-Sheet 2 Filed July 12, 1968 POWER SUPPLY az laln/ ATTORNEY United States Patent 3,541,823 ELECTROMAGNETIC FORMING APPARATUS Richard Weadock, Jr., Saginaw, Mich., assignor to General Motors Company, Detroit, Mich., a corporation of Delaware Filed July 12, 1968, Ser. No. 744,566 Int. Cl. B21d 26/14 US. Cl. 72-56 1 Claim ABSTRACT OF THE DISCLOSURE The combination of a primary coil and a plurality of relatively movable secondary coils arranged so as to alternately define a workspace for the workpiece and a clearance space through which the workpiece may be laterally transferred into and out of the workspace.

This invention relates to apparatus for electromagnetically forming a workpiece, and more particularly to electromagnetic forming apparatus wherein the workpiece may be laterally inserted within and removed from the workspace.

Typically, present electromagnetic forming apparatus includes a primary coil located in electromagnetic coupling relationship with one or more secondary coils which define a workspace for the workpiece. The primary coil is energized so as to generate a magnetic field which in turn energizes the secondary coils thereby producing a more intense magnetic field within the workspace so as to impose a forming force on the workpiece.

In order to obtain optimum electromagnetic coupling, the primary coil is usually located adjacent the secondary coils thereby presenting an obstruction which prohibits the transfer of the workpiece into and out of the workspace in a lateral direction with respect to the workspace. The problem is especially acute Where the workpiece includes an extended portion which protrudes outwardly from the workspace. Consequently, the workpiece must ordinarily be installed within and withdrawn from the workspace by transferring it axially with respect to the workspace. The requirement that the workpiece be axially indexed into and out of the workspace has made the electromagnetic forming process generally unsuitable for use with automatic transfer equipment of the type which requires that the workpiece be transferred laterally with respect to the workspace.

Accordingly, it is a principal object of this invention to provide an electromagnetic forming apparatus wherein the workpiece may be laterally transferred into and out of the workspace. It is another object of this invention to provide an electromagnetic forming apparatus including the combination of a primary coil and a plurality of relatively movable secondary coils arranged so as to alternately define a workspace for the workpiece and a clearance space through which the workpiece may be laterally inserted within and removed from the workspace. It is a further object of this invention to provide an electromagnetic forming apparatus which is particularly adaptable for use with automatic transfer equipment of the type which requires that the workpiece be indexed laterally with respect to the workspace.

In order to accomplish these and other objects, the preferred embodiments of the inventive apparatus comprise a primary coil and a plurality of relatively movable secondary coils. The primary coil includes a plurality of shaped segments which are integrally connected so as to provide an opening between the shaped segments. The secondary coils are maneuvered between a converged position and a retracted position by a pair of drive motors. In the converged position, a workspace for the workpiece is provided between the secondary coils. In the retracted position, an opening is provided between the secondary coils which is aligned with the Opening within the primary coil so as to define a clearance space extending laterally across the workspace so that the workpiece may be laterally transferred into and out of the workspace by passing it through the clearance space.

The invention may best be understood by reference to the following detailed description of the preferred embodiments when considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of one embodiment of the electromagnetic forming apparatus of the invention.

FIG. 2 is another perspective view of the electromagnetic forming apparatus illustrated in FIG. 1.

FIG. 3 is an exploded view of the electromagnetic forming apparatus illustrated in FIGS. 1 and 2.

FIG. 4 is a schematic diagram of a current source which may be employed in cooperation with the electromagnetic forming apparatus of the invention.

FIG. 5 is an exploded view of another embodiment of the electromagnetic forming apparatus of the invention.

FIG. 6 is an exploded view of yet another embodiment of the electromagnetic forming apparatus of the invention.

With reference to FIGS. 1, 2 and 3, one embodiment of the electromagnetic forming apparatus of the invention is disclosed. The illustrated apparatus comprises a multiple turn primary coil 10, two single turn secondary coils 12 and 14, and a pair of drive motors 16 and 18.

Referring particularly to FIG. 3, a workpiece 20 comprises a tubular member 22 and a shaft member 24 having a hub portion 25 onto which the end of the tubular member 22 is to be clamped by the application of an electromagnetic forming force. As will be readily understood, the inventive apparatus may be employed to electromagnetically form a variety of different workpieces other than the workpiece '20 which is shown for demonstration purposes only.

The multiple turn primary coil 10 is provided by a continuous flat wound ribbon conductor 26 which is embedded within a coil support member 28. Preferably, the ribbon conductor 26 is made of a highly conductive material such as copper and the coil support member 28 is made of a good insulating material such as an epoxy filled fiber glass. The primary coil 10 includes two parallel spaced I-shaped segments 30 and 32 and a U- shaped segment 34. The I-shaped segments 30 and 32 lie approximately within a first plane X-Z. The U-shaped segment 34 lies approximately within a second plane X-Y which is substantially perpendicular to the first plane X-Z. The I-shaped segments 30 and 32 include ends 36 and 38, respectively. The U-shaped segment 34 includes a pair of ends 40 and 42. The ends 36 and 38 of the I-sha-ped segments 30 and 32 are merged with the ends 40 and 42, respectively, of the U-shaped segment 34. Thus, one of the ends of each of the I-shaped segments 30 and 32 is integrally connected with a different one of the ends of the U-shaped segment 34.

An opening 44 is provided within the primary coil 10 between the I-shaped segments 30 and 32 and the U-shaped segment 34. The primary coil 10 also includes a pair of input terminals 46 and 48. The ribbon conductor 26 may have any desired number of turns and may be wound in any desired manner so long as the general shape of the primary coil 10 is as previously described.

The single turn secondary coils 12 and 14 are provided by a pair of plate conductors 50 and 52 having formed edge portions 54 and 56, respectively. Preferably, the plate conductors 50 and 52 are made of a highly conductive material such as copper. The driven motors 16 and 18 are rigidly connected to the secondary coils 12 and 14, respectively, so as to maneuver them with respect to the primary coil and with respect to each other between a converged position as shown in FIG. 1 and a retracted position as shown in FIG. 2. The drive motors 16 and 18 may be any suitable pneumatic, hydraulic or electric motors.

Referring to FIG. 1, with the secondary coils 12 and 14 in the converged position, a Workspace 58 is provided between the formed edge portions 54 and 56. The secondary coils 12 and 14 are located in electromagnetic coupling relationship with the I-shaped segments 30 and 32, respectively, of the primary coil 10. An insulating strip 60 electrically isolates the secondary coils 12 and 14 in the converged position. The insulating strip 60 may be attached to either of the secondary coils 12 and 14.

Referring to FIG. 2, with the secondary coils 12 and 14 in the retracted position, an opening 62 is provided between them. The opening 62 is aligned with the opening 44 provided within the primary coil 10 so that together the openings 44 and 62 define a clearance space 64 which extends laterally across the workspace 58. Thus, when the secondary coils 12 and 14 are in the retracted position, the workpiece may be laterally inserted within and removed from the workspace 58 by passing it through the clearance space 64 as indicated by the arrow 66. The clearance space 64 adequately accommodates the shaft member 24 of the workpiece 20.

FIG. 4 illustrates a current source which may be used in cooperation with the inventive electromagnetic forming apparatus shown in FIGS. 1, 2 and 3. The current source includes a high voltage power supply 68, a manually operable power switch 70, a capacitor bank 72, and a spark gap 74. As will be readily appreciated, various other types of current sources may be employed. For example, the capacitor bank 72 may be replaced by a motor-generator set, and the spark gap 74 may be replaced by a thyratron or an ignitron. The current source also includes a pair of output terminals 76 and 78 which are adapted to be connected to the input terminals 46 and 48, respectively, of the primary coil 10.

The electrical operation of the inventive electro-magnetic forming appartus illustrated in FIGS. 1, 2 and 3 may be best understood by referring to FIGS. 3 and 4. When the manually operable switch 70 is closed, current at the voltage of the power supply 68, for example 10 kilovolts, is supplied to the capacitor bank 72. The capacitor bank 72 then charges to some predetermined voltage at which the spark gap 74 ionizes and becomes conductive.

As the spark gap 74 conducts, a high energy current of short duration, for instance 100,000 amperes for 30 microseconds, is supplied to the primary coil 10 as indicated by the arrows 80. The primary current 80 flows through the I-shaped segments 30 and 32 where it generates a high intensity magnetic field, as denoted by the arrows 82, between the primary coil 10 and the secondary coils 12 and 14. The magnetic field 82 induces large currents in the secondary coils 12 and 14 as indicated by the arrows 84 and 86, respectively. The secondary currents 84 and 86 circulate near the outer periphery of the secondary coils 12 and 14, including the formed edge portions 54 and 56. A very high intensity magnetic field, as denoted by the arrows 88, is generated within the workspace 58 by the secondary currents 84 and 86 so as to impose an electromagnetic forming force on the workpiece 20.

As will be readily apparent, the multiple turn primary coil 10 and the single turn secondary coils 12 and 14 act as a transformer combination so that there is a decrease in the voltage and an increase in the current transferred between them. Therefore, the secondary currents 84 and 86 flowing around the formed edge portions 54 and 56 of the secondary coils 12 and 14 are much larger than the primary current 80 flowing through the primary coil 10. correspondingly, the magnetic field 88 generated by the secondary currents 84 and 86 is much more intense than the magnetic field 82 generated by the primary current 80. Thus, the primary coil 10 is energized so as to produce a high intensity magnetic field 82 which, in turn, energizes the secondary coils 12 and 14 thereby producing a very high intensity magnetic field 88 within the workspace 58 so as to impose a forming force on the workpiece 20.

Referring to FIG. 5, another embodiment of the invention is disclosed. The illustrated electromagnetic forming apparatus is identical in structure to that shown in FIGS. 1, 2 and 3 except for the general shape of the primary coil 10, and like numerals are used to denote like elements. The primary coil 10 includes a first pair of parallel spaced U-shaped segments 90 and 92 and a second pair of parallel spaced U-shaped segments 94 and 96. The U-shaped segment 90 lies approximately within a first plane X-Y and the U-shaped segment 92 lies approximately within a second plane XY which is substantially parallel to the first plane X-Y. The U-shaped segments 94 and 96 both lie approximately within a third plane X-Z which is substantially perpendicular to the first plane X-Y and the second plane XY'. The U-shaped segment 90 includes a pair of ends 98 and 100 while the U-shaped segment 92 includes a pair of ends 102 and 104. The U-shaped segment 94 includes a pair of ends 106 and 108 while the U-shaped segment 96 includes a pair of ends 110 and 112.

The ends 106 and 108 of the U-shaped segment 94 are merged with the ends 98 and 102, respectively, of the U-shaped segments 90 and 92. The ends 110 and 112 of the U-shaped segment 96 are merged with the ends 100 and 104, respectively, of the U-shaped segments 90 and 92. Thus, one of the ends of each of the U-shaped segments 94 and 96 of the second pair is integrally connected with a different one of the ends of one of the U-shaped segments 90 and 92 of the first pair, and the other one of the ends of each of the U-shaped segments 94 and 96 of the second pair is integrally connected with a different one of the ends of the other of the U-shaped segments 90 and 92 of the first pair. When the secondary coils 12 and 14 are in the converged position, they are in electromagnetic coupling relationship with the U-shaped segments 94 and 96 of the second pair, respectively. When the secondary coils are in the retracted position, the opening 44 provided within the primary coil between the U-shaped sections 90, 92, 94 and 96 is aligned with the opening 62 provided between the secondary coils 12 and 14 so as to define the clearance space 64. The mechanical and electrical operation of the inventive apparatus illustrated in FIG. 4 is substantially identical to that previously described with respect to the inventive apparatus shown in FIGS. 1, 2 and 3.

Referring to FIG. 6, yet another embodiment of the invention is disclosed. Again, the illustrated electromagnetic forming apparatus is identical in structure to that shown in FIGS. 1, 2 and 3 except for the general shape of the primary coil 10, and like numerals are used to denote like elements. The primary coil 10 includes a C-shaped segment 114 and a U-shaped segment 116. The C-shaped segment 114 lies approximately within a first plane X-Y and the U-shaped segment 116 approximately within a second plane X-Z which is substantially perpendicular to the first plane X-Y. The C-shaped segment 114 includes a pair of ends 118 and 120. The U-shaped segment 116 includes a pair of ends 122 and 124. The ends 118 and 120 of the C-shaped segment are merged with the ends 122 and 124, respectively, of the U-shaped segment 116. Thus, each one of the ends of the C-shaped segment 114 is integrally connected with a diiferent one of the ends of the U-shaped segment 116. When the secondary coils 12 and 14 are in the converged position, they are in electromagnetic coupling relationship with the C-shaped segment 114. When the secondary coils 12 and 14 are in the retracted position, the opening 44 provided within the primary coil 10 between the C- shaped section 114 and the U-shaped section 116 iS aligned with the opening 62 provided between the secondary coils 12 and 14 so as to define the clearance space 64. Again, the mechanical and electrical operation of the inventive apparatus illustrated in FIG. 6 is substantially identical to that previously described with respect to the inventive apparatus shown in FIGS. 1, 2 and 3.

It will now be readily apparent that a principal advantage of the apparatus of the invention is that it permits the workpiece to be transferred laterally with respect to the workspace. The capability of laterally transferring the workpiece into and out of the workspace makes the inventive apparatus particularly adaptable for use with automatic transfer equipment of the type which requires that the workpiece be indexed laterally with respect to the workspace.

It is to be understood that the preferred embodiments of the invention described herein are merely illustrative and the various alterations and modifications may be made without departing from the spirit and scope of the invention which is to be limited only by the following claim.

I claim:

1. An apparatus for electromagnetically forming a conductive workpiece, comprising: a primary ribbon conductor shaped so as to provide a pair of parallel spaced generally I-shaped segments and a generally U-shaped segment, the I-shaped segments lying approximately within a first plane and the U-shaped segment lying approximately within a second plane substantially perpendicular to the first plane, one of the ends of each of the I-shaped segments integrally connected with a different one of the ends of the U-shaped segment so as to define a workpiece transfer opening extending laterally between the I-shaped segments and through the U-shaped segment; a pair of secondary plate conductors each having a formed edge portion, the secondary conductors so disposed with respect to each other that when they are in a converged position the secondary conductors are located in relatively adjacent electrically isolated relationship so as to define a workspace for the workpiece between the formed edge portions and when they are in a retracted position the secondary con- 6 ductors are located in relatively distant spaced relationship so as to define a workpiece transfer opening extending laterally between the formed edge portions, the secondary conductors further so disposed with respect to the primary conductor that when they are in the converged position the secondary conductors are each located in relatively adjacent electromagnetic coupling relationship with a dilferent one of the I-shaped segments of the primary conductor and when they are in the retracted position the secondary conductors are each located in relatively adjacent aligned relationship with a different one of the I-shaped segments of the primary conductor so that the workpiece transfer opening pro vided between the formed edge portions of the secondary conductors and the workpiece transfer opening provided between the shaped segments of the primary conductor are contiguous thereby to define a workpiece clearance space extending laterally across the workspace; means for maneuvering the secondary conductors into the converged position so that a forming force may be imposed upon a workpiece positioned within the workspace, and for maneuvering the secondary conductors into the retracted position so that a workpiece may be inserted within and removed from the workspace by unidirectionally transferring it through the workpiece clearance space; and means for energizing the primary conductor thereby energizing the secondary conductors to produce a high intensity time varying magnetic field for imposing a forming force on a workpiece position within the workspace.

References Cited UNITED STATES PATENTS 3,210,509 10/1965 Alf 7256 3,258,573 6/1966 Morin et a1. 7256 3,383,890 5/1968 Wildi 7256 3,391,558 7/1968 Deeg 72-56 3,423,978 1/1969 Kline 7256 RICHARD J. HERBST, Primary Examiner U.S. Cl. X.R. 72-706 

